Edited Readme added testing information
Edited Readme added testing information

Added note stating what OS the template was tested with and noting
that the sample application does not work with Xenial.

Change-Id: Ia6b2e37b8614ff7b5a44a5fff9c46566c67a2bb5

openstack/osops-tools-contrib,openstack/osops-tools-contrib,openstack/osops-tools-contrib,openstack/osops-tools-contrib